5. Error handling and even successful termination is very, very easy to get wrong with nested callbacks (forgetting to call a callback, or forgetting to catch u

5. Error handling and even successful termination is very, very easy to get wrong with nested callbacks (forgetting to call a callback, or forgetting to catch unexpected exceptions and pass them to the callback, means the function never returns at best or brings down the whole process at worst). Promises make this much easier by automatically propagating errors for you down the promise chain (though you or your caller do still need to handle the error at the end of the chain).